1. Field of the Invention
The present invention relates to an organic electroluminescent element manufacturing method.
2. Description of the Related Art
Recently, an organic electroluminescent element (hereinafter it is referred to as an organic EL element) has been receiving attention as a flat display element in the next generation display apparatuses.
In general, the organic EL element includes: a first electrode; a buffer layer (a hole transport layer, a hole injection layer, or the like) provided on the first electrode; a light emitting layer provided on the buffer layer; and a second electrode provided on the light emitting layer. While the light emitting layer has comparatively low conductivity, the buffer layer has comparatively high conductivity in general. For this reason, when the buffer layer is in direct contact with the second electrode, the second electrode becomes conducting to the first electrode to generate leakage current, thereby lowering the light emitting efficiency. In view of this, the light emitting layer must be formed so as to cover the buffer layer completely. Nevertheless, in the case where the buffer layer and the light emitting layer are formed by ink-jetting, a part of the buffer layer may be exposed from the light emitting layer according to the discharge amount of an ink, which means that the buffer layer may be covered with the light emitting layer only partially or not completely.
To tackle the above problem, for example, in WO 01/074121, a film formation region of the light emitting layer is made larger than the a film formation region of the hole transport layer by setting the amount of the light emitting layer forming ink to be larger than that of the hole transport layer forming ink.
Even in the case where the amount of the light emitting layer forming ink is set larger than that of the hole transport layer forming ink (an ink for forming the buffer layer), however, the film formation region of the light emitting layer becomes not necessarily larger than the film formation region of the buffer layer, and therefore, the buffer layer may be covered with the light emitting layer partially or not completely. Accordingly, in order to attain a condition where the buffer layer is covered with the light emitting layer completely, a test must be repeated in which organic EL elements are manufactured actually with the discharge amounts of the inks changed and leakage current is measured. This increases the manufacturing cost of the organic EL element.